The spherical shape grinding body for drum mills is widely known and used in practice. A disadvantage of the spherical grinding body is the low productivity of mills, slow crushing of materials because of the absence of edges and low level of stuffing of the working space.
Patents DE 440 198/1927, FR 811 408/1937, SU 1 388 088/1985, RU 2 305 597/2005 describe a grinding body of tetrahedron shape with flat or rounded faces, which have the disadvantage to be not easy and cheap for mass-production and for that reason have not been practically used yet.
An International patent application WO/2010/094091 describes a tetrahedron grinding body that overcomes the difficulties and high cost of its production.
A cubic shape grinding body is also known—U.S. Pat. No. 1,431,475/1920, which has not been used because of expensive and difficult production as well as worse milling results shown compared to the spherical grinding body.